From subduction- to strike slip-related volcanism: Sr-Nd-Pb isotope and geochronology of lavas from Sivas-Malatya region, Central-Eastern Anatolia

Anatolia is characterised by a complex geodynamic evolution, mirrored by a wide spectrum of magmatism. Here we investigated the timing and the geochemical/isotopic characters of the Miocene to Pliocene volcanism of Sivas-Malatya Region (Central-Eastern Anatolia), and its relationships with local and regional tectonics. Na-alkaline basaltic lavas were emplaced during middle Miocene at Sivas (16.7-13.1 Ma), in the North, whilst transition from calc-alkaline to Na-alkaline rocks is observed at Yamadağ and Kepez Dağ volcanic complexes. Calc-alkaline products erupted during Early to Middle Miocene, and more precisely from 19.5 to 13.6 Ma at Yamadağ and from 16.4 to 14.1 Ma at Kepez Dağ, with final Na-alkaline final activity of the Arguvan volcanic field lasting till Late Miocene (15.7 - 10.6 Ma). Volcanism renewed during the Pliocene in the Kangal (5.9-4.0 Ma) volcanic field with the emission of K-alkaline igneous rocks. Mafic calc-alkaline and Na-alkaline rocks partially overlap in age but can be easily distinguished by their petrochemical characters. Mafic calc-alkaline igneous rocks show typical subduction-related petrological and geochemical affinities. They are both two-pyroxene and clinopyroxene-bearing rocks, and characterised by high LILE/HFSE values, with variable 87Sr/86Sri (0.70396-0.70539) and 143Nd/144Ndi (0.51260-0.51287). Mafic Na-alkaline igneous rocks show intraplate petrological and geochemical flavours although some HFSE depletion with respect to LILE, as well as variable 87Sr/86Sri (0.70347-0.70553) and 143Nd/144Ndi (0.51261-0.51291) isotopic compositions are present. These characteristics are strongly suggestive for the occurrence, at some stage of their genesis, of a possible interaction with subduction-related reservoirs. The Kangal K-alkali basalts still show intraplate-like petrological and geochemical affinities with HFSE/LILE ratios similar to those of the Miocene Na-alkaline rocks, and largely variable 87Sr/86Sri (0.70425-0.70520) and 143Nd/144Ndi (0.51262-0.51277) isotopic compositions, overlapping the arrays observed in the earlier stages of volcanism. A general transition from calc-alkaline to Na-alkaline volcanic rocks is observed with time, according with the evolution of the geodynamics of the Anatolia region. Early to Middle Miocene calc-alkaline magmas were derived by partial melting of the mantle wedge delimited by the subduction last oceanic branch of the Neotethys. The Na-alkaline magmas, on the other hand, were generated within the asthenospheric mantle beneath the slab and migrated through slab tears into the mantle wedge where mixed with subduction-related components. The subduction-related component decreased with time until to form clear within-plate lavas found in the Arguvan volcanic field. The appearance of the youngest K-alkaline volcanic rocks in the Kangal basin represents an abrupt change in the magma supply at depth, although continental crustal contamination en-route to the surface played an important role in their genesis.